Field of the Invention
The present invention relates to a one component spray polyurethane foam formulation that achieves a B2 rating in DIN 4102 testing and that is suitable for use in sealing fenestration openings.
Introduction
Fenestration openings in building structures offer challenging locations for insulation. Fenestration openings typically have gaps between the fenestration frames and the supporting structure around the fenestration opening. The gaps are a source of energy leakage if they are not sealed and insulated. Polymeric spray foam insulation/sealant is a common and convenient choice for filling these fenestration gaps. In particular one component spray polyurethane foam (OCF) is a desirable choice for insulating fenestration gaps.
Fenestration gaps provide technical challenges for insulation/sealants. To seal the fenestration gap, the insulation/sealant must adhere to the structural materials defining the gap and remain adhered to those structural materials as they undergo thermal expansion and contraction with weather changes and structural shifts as the building structure settles. Therefore, the structural adhesive must be an adhesive material, but must also be a flexible material.
For convenience in application, it is desirable for the insulation/sealant to be a spray foam material, more particularly a OCF formulation to avoid difficulties associated with metering multiple components such as is required in two-component spray polyurethane foam formulations. At the same time, the foam formed by the OCF formulation needs to be sufficiently flexible not only to move with the structural materials to which it adheres, but also to conform to the gap spacing without deforming the structural members defining the gap. If a spray foam formulation forcefully expands into a rigid foam, the expansion can move the structural materials defining the gap and thereby cause fenestrations intended to fit within a fenestration opening to no longer fit in the opening properly.
The OCF should form an open-cell foam structure to allow blowing agent to escape from the foam and to allow moisture to escape from fenestration gaps, but at the same time inhibit excessive airflow so as to fail to have insulating properties. Therefore, it is desirable for a foam to have an air flow rate between 0.001 liters per second (L/s) and 0.02 L/s as determined by ASTM D3574.
A great deal of research and development has gone into identifying a OCF formulation that meets these requirements for use as a fenestration gap insulator/sealant. See, for example, WO2014/033231A1 and WO 02/12367A1 for two published patent applications that provide proposed solutions to OCF formulations for use in fenestration gaps.
An added challenge for OCF fenestration insulation/sealant materials is a need now to achieve certain flame retardant performance to meet code restriction. In particular, it is required for the OCF to achieve a B2 rating in DIN 4102 testing in some countries. Examples In WO2014/033231A1 show that a B2 rating is only achieved when the foam contains more than 12 weight-percent halogen (bromine plus chlorine) based on foam formulation weight. It is desirable to find a way to achieve a B2 rating without requiring so much halogen in the foam. WO2010/058036 describes a OCF that contains expandable graphite to enhance flame retardant properties. However, expandable graphite is a solid particulate that can complicate dispensing of OCF formulation by plugging openings in dispensing means used to apply the OCF formulation. Therefore, it is desirable to avoid using expandable graphite in a OCF formulation.
It is desirable and would advance the art of OCF technology to discover a OCF formulation that produces a flexible, open-celled foam and that achieves a B2 flame retardancy rating in DIN 4102 testing without containing expandable graphite and while containing less than 12 weight-percent halogen based on formulation weight.